Automotive power electronics systems for use in electric cars and hybrid cars are mainly constituted of a battery that supplies DC power, an inverter that performs DC-to-AC conversion, and a motor that obtains drive force from the electrical output of the inverter. The inverter in this case is a power conversion device.
The power conversion device incorporates switches formed of power semiconductor elements and, in the case of an inverter, converts DC power into AC power by opening and closing the switches and, in the case of a converter, converts the voltage by opening and closing the switches.
There are cases where the voltage fluctuation resulting from the opening and closing of the switches is radiated as a common mode noise and adversely affects the listening of the in-vehicle radio and other digital instruments. To solve this, in a conventional practice, a line that supplies power to the power conversion device and a grounding surface are connected by a capacitor to discharge the common mode noise to the ground potential (Patent Literature 1, for example).